In certain industrial processes, such as the drawing and crimping of synthetic yarn tow and the like, and in other similar industrial processes, a substantial amount of steam, vapors, smoke, and or oil fumes, hereinafter sometimes referred to as "exhaust gases," are generated. It is of course necessary to collect these gases and not let them escape into the atmosphere of the work room surrounding the machines. It has become commonplace to use an exhaust hood over such work areas, which, while substantially removing the contaminated exhaust gases, also draws in a tremendous amount of the conditioned air from the work room surrounding the textile machines. This conditioned air (either heated in winter or cooled in summer) is expensive to treat, and therefore costs of conditioning air can be minimized if the exhaust gases can be removed without, at the same time, losing the conditioned air into the exhaust hood.
There are several relatively elaborate and expensive schemes and systems for controlling these exhaust gases, as noted in the prior art U.S. Pat. to Danieli No. 3,834,293; to Laube U.S. Pat. No. 3,708,414; and to Tavan U.S. Pat. No. 3,303,839. While the apparatus described in each of these patents is satisfactory for its own purpose, they do not substantially solve the problem described hereinabove. For example, the Danieli patent is illustrative of an extremely large and elaborate system for completely encircling a smelting furnace work area with a screen of compressed air from floor to ceiling. Such an air screen, while disposing of the gases from the smelting furnace in a suitable manner, will also tend to remove a substantial amount of treated air from the room surrounding the furnace. In work areas where smelting occurs this may be immaterial, but in air conditioned work rooms (heated or cooled), it becomes very important.
In the Laube patent, an air curtain which also completely surrounds the work station is generated in an inclined path over a considerable distance, again to remove exhaust gases from an electrolytic melt vessel. The Tavan patent is directed to a cooking unit which includes a vertical air curtain completely surrounding the unit, however the air supplied is drawn from the room surrounding the cooking unit, passed through the air curtain, and collected where it is filtered and then returned into the room.